Low friction tape head

ABSTRACT

A drive-implemented method according to one embodiment includes guiding a magnetic medium over a magnetic head at an angle at which the magnetic medium flies over a leading outer portion of the head, engages a leading edge of a tape bearing surface of a central portion of the head, and engages an inner edge of a tape bearing surface of a trailing outer portion of the head. The inner edge of the tape bearing surface of the trailing outer portions skives air from the magnetic medium when the magnetic medium travels in a direction from the central portion towards the trailing outer portion.

BACKGROUND

The present invention relates to data storage systems, and moreparticularly, this invention relates to a low friction tape head.

Business, science and entertainment applications depend upon computersto process and record data, often with large volumes of the data beingstored or transferred to nonvolatile storage media, such as magneticdiscs, magnetic tape cartridges, optical disk cartridges, floppydiskettes, or floptical diskettes. Typically, magnetic tape is the mosteconomical and convenient means of storing or archiving the data.Storage technology is continually pushed to increase storage capacityand storage reliability. Improvement in data storage densities inmagnetic storage media, for example, has resulted from improved mediummaterials, improved magnetic read/write heads, improved error correctiontechniques and decreased areal bit sizes. The data capacity of half-inchmagnetic tape, for example, is now measured in thousands of gigabytes on2000 or more data tracks.

An important and continuing goal in the data storage industry is that ofincreasing the density of data stored on a medium. For tape storagesystems, that goal has led to increasing the track density on recordingtape, and decreasing the thickness of the magnetic tape medium. However,the development of higher performance tape drive systems has createdvarious problems in the design of a tape head assembly for use in suchsystems.

For example, in the quest to develop tape media, the tape media having athinner magnetic coating, the tape media has become smoother. However,smoother tape media has resulted in higher levels of static and runningfriction on the head. To exemplify, consider that in a tape drivesystem, a magnetic tape is moved over the surface of the tape head athigh speed. If the tape is rough, this movement generally entrains afilm of air between the head and tape. However, smoother tape media doesnot entrain as much air, resulting in more intimate contact between headand tape thereby increasing running friction.

Static friction, also known as “stiction,” at the head-tape interface ofa tape drive can be a significant issue. The stiction forces for smoothtapes can be so high that a drive cannot cause the tape medium to comefree from the head. If excessive force is used to move the tape, thetape may become damaged or even break.

Solutions for the friction problem, such as, head patterning have beenproposed, but such solutions add cost to existing tape drives.

BRIEF SUMMARY

A drive-implemented method according to one embodiment includes guidinga magnetic medium over a magnetic head at an angle at which the magneticmedium flies over a leading outer portion of the head, engages a leadingedge of a tape bearing surface of a central portion of the head, andengages an inner edge of a tape bearing surface of a trailing outerportion of the head. The inner edge of the tape bearing surface of thetrailing outer portions skives air from the magnetic medium when themagnetic medium travels in a direction from the central portion towardsthe trailing outer portion.

A method for setting a wrap angle according to one embodiment includesadjusting a guide position to overwrap a magnetic tape over an outeredge of a leading outer potion of a magnetic head having the leadingouter portion, a trailing outer portion, and a central portionpositioned between the outer portions, each portion having a tapebearing surface and an array of transducers selected from a groupconsisting of readers and writers; causing the magnetic tape to passover the head, the tape traveling in a direction from the leading outerportion towards the trailing outer portion; causing reading of themagnetic tape using the leading outer portion; adjusting a wrap angle ofthe magnetic tape relative to the leading outer portion until the tapeis no longer readable; determining a position of the guide when the tapebecomes no longer readable; selecting a wrap angle based on thedetermined position of the guide; and setting the guide to provide theselected wrap angle.

Any of these embodiments may be implemented in a magnetic data storagesystem such as a tape drive system, which may include a magnetic head, adrive mechanism for passing a magnetic medium (e.g., recording tape)over the magnetic head, and a controller electrically coupled to themagnetic head.

Other aspects and embodiments of the present invention will becomeapparent from the following detailed description, which, when taken inconjunction with the drawings, illustrate by way of example theprinciples of the invention.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

For a fuller understanding of the nature and advantages of the presentinvention, as well as the preferred mode of use, reference should bemade to the following detailed description read in conjunction with theaccompanying drawings.

Prior Art FIG. 1 illustrates a traditional flat-lapped magnetic tapehead, in accordance with the prior art.

Prior Art FIG. 2 is an enlarged view of Circle 2 of FIG. 1, showing afirst known effect associated with the use of the head of FIG. 1.

FIG. 3 is a side view of a magnetic tape head with three portionsaccording to one embodiment of the present invention.

FIG. 4 is a side view of a magnetic tape head with three portions in useaccording to one embodiment of the present invention.

FIG. 5 is a side view of a magnetic tape head with three portions in useaccording to one embodiment of the present invention.

FIG. 6 is a tape bearing surface view of a portion of a tape head havingpatterning according to one embodiment.

FIG. 7 is a cross sectional view taken from Line 7-7 of FIG. 6.

FIG. 8 is a schematic diagram of the tape drive system.

DETAILED DESCRIPTION

The following description is made for the purpose of illustrating thegeneral principles of the present invention and is not meant to limitthe inventive concepts claimed herein. Further, particular featuresdescribed herein can be used in combination with other describedfeatures in each of the various possible combinations and permutations.

Unless otherwise specifically defined herein, all terms are to be giventheir broadest possible interpretation including meanings implied fromthe specification as well as meanings understood by those skilled in theart and/or as defined in dictionaries, treatises, etc.

It must also be noted that, as used in the specification and theappended claims, the singular forms “a,” “an” and “the” include pluralreferents unless otherwise specified.

The following description discloses several preferred embodiments oftape-based storage systems, as well as operation and/or component partsthereof.

In one general embodiment, a magnetic data storage system includes amagnetic head; and guides on opposite sides of the magnetic head fordirecting a magnetic medium over the magnetic head. The magnetic headincludes: outer portions each having a tape bearing surface and an arrayof transducers selected from a group consisting of readers and writers;and a central portion positioned between the outer portions, the centralportion having a tape bearing surface and an array of transducersselected from a group consisting of readers and writers. An inner edgeof each of the tape bearing surfaces of the outer portions is adaptedfor skiving air from the magnetic medium when the magnetic mediumtravels in a direction from the central portion towards the respectiveouter portion. The guides are oriented to direct the magnetic medium tofly over a leading one of the outer portions, engage a leading edge ofthe tape bearing surface of the central portion, and engage an inneredge of the tape bearing surface of a trailing one of the outerportions.

In another general embodiment, a magnetic head includes outer portionseach having a tape bearing surface and an array of transducers selectedfrom a group consisting of readers and writers; and a central portionpositioned between the outer portions, the central portion having a tapebearing surface and an array of transducers selected from a groupconsisting of readers and writers. The outer edges of the tape bearingsurfaces of the outer portions are non-skiving, and an inner edge ofeach of the tape bearing surfaces of the outer portions is adapted forskiving air from the magnetic medium when the magnetic medium travels ina direction from the central portion towards the respective outerportion.

In another general embodiment, a method includes guiding a magneticmedium over a magnetic head at an angle at which the magnetic mediumflies over a leading outer portion of the head, engages a leading edgeof a tape bearing surface of a central portion of the head, and engagesan inner edge of a tape bearing surface of a trailing outer portion ofthe head. The inner edge of the tape bearing surface of the trailingouter portions skives air from the magnetic medium when the magneticmedium travels in a direction from the central portion towards thetrailing outer portion.

In yet another general embodiment, a method for setting a wrap angleaccording to one embodiment includes adjusting a guide position tooverwrap a magnetic tape over an outer edge of a leading outer potion ofa magnetic head having the leading outer portion, a trailing outerportion, and a central portion positioned between the outer portions,each portion having a tape bearing surface and an array of transducersselected from a group consisting of readers and writers; passing themagnetic tape over the head, the tape traveling in a direction from theleading outer portion towards the trailing outer portion; reading themagnetic tape using the leading outer portion; adjusting a wrap angle ofthe magnetic tape relative to the leading outer portion until the tapeis no longer readable; determining a position of the guide when the tapebecomes no longer readable; selecting a wrap angle based on thedetermined position of the guide; and setting the guide to provide theselected wrap angle.

FIG. 1 illustrates a traditional flat-lapped bi-directional, two-modulemagnetic tape head 100, in accordance with the prior art. As shown, thehead includes a pair of bases 102, each equipped with a module 104. Thebases are typically “U-beams” that are adhesively coupled together. Eachmodule includes a substrate 104A and a closure 104B with readers andwriters 106 situated therebetween. In use, a tape 108 is moved over themodules along a tape bearing surface 109 in the manner shown for readingand writing data on the tape using the readers and writers.Conventionally, a partial vacuum is formed between the tape and the tapebearing surface for maintaining the tape in close proximity with thereaders and writers.

Two common parameters are associated with heads of such design. Oneparameter includes the tape wrap angles α_(i), α_(o) defined between thetape and a plane 111 in which the upper surface of the tape bearingsurface resides. It should be noted that the tape wrap angles α_(i),α_(o) include an inner wrap angle α_(i) which is often similar in degreeto an external, or outer, wrap angle α_(o). The tape bearing surfaces ofthe modules are set at a predetermined angle relative to each other suchthat the desired inner wrap angle α_(i) is achieved at the facing edges.Moreover, a tape bearing surface length 112 is defined as the distance(in the direction of tape travel) between opposite edges of the tapebearing surface.

During use of the head of FIG. 1, various effects traditionally occur.FIG. 2 is an enlarged view of the area encircled in FIG. 1. FIG. 2illustrates a first known effect associated with the use of the head 100of FIG. 1. When the tape 108 moves across the head as shown, air isskived from below the tape by a skiving edge 204 of the substrate 104A,and instead of the tape 108 lifting from the tape bearing surface 109 ofthe module (as intuitively it should), the reduced air pressure in thearea between the tape and the tape bearing surface results from skivingand causes atmospheric pressure to urge the tape towards the tapebearing surface.

A problem with such designs is that running friction is added at eachlocation where the tape wraps an edge, i.e., the four edges of themodules of FIG. 1. Particularly, at each wrapped edge, the contactpressure between the head and the tape is higher, resulting in higherrubbing friction. That ultimately requires more energy to pull the tapeacross the head. Moreover, multiple wraps put more stress on the tapeand cause more tape wear.

Possibly the worst effect of wrapping the corners is that it can launchacoustic waves in the tape. Without wishing to be bound by any theory,it is believed that when asperities on the tape engage the skiving edgesof the head, the tape tends to stick momentarily and then break free,thus launching the acoustic waves. The waves, in turn, causes thevelocity of the tape at the head-tape interface to oscillate. Again,without wishing to be bound by any theory, the acoustic wave is acompressional wave running in the plane of the tape, resulting in astanding wave between tape supports and causing the tape velocity tooscillate at the head-tape interface. Though the resultant jitter at thetape-head interface is small, it is enough to cause detection problems.When the tape is running very slowly, this effect becomes morenoticeable.

FIG. 3 illustrates a magnetic data storage system 300 according to oneembodiment of the present invention that includes a magnetic head 302and guides 304, 306 on opposite sides of the magnetic head for directinga magnetic medium 308 over the magnetic head. In the embodiment shown,the magnetic medium is a tape medium.

The magnetic head includes outer portions 310, 312, each having a tapebearing surface 314, 315 that is preferably flat lapped, and an array oftransducers selected from a group consisting of readers and writers ofany type, including those known in the art. A central portion 316 ispositioned between the outer portions. The central portion also has atape bearing surface and an array of transducers selected from a groupconsisting of readers and writers.

In FIG. 3, the medium is shown extending across the head and at rest(not in motion). The medium rests on the tape bearing surface of thecentral portion, and has minimal contact with the inner edges 318, 320of each of the tape bearing surfaces of the outer portions. The positionof the inner edges of each of the tape bearing surfaces of the outerportions relative to the plane of the tape bearing surface of thecentral portion determines the tape wrap angle between the plane of thetape and the tape bearing surface of the central portion. Anillustrative tape wrap angle is between about 0.5° to about 2°.

Referring to FIG. 4, the medium is shown travelling from left to right.The angle β (FIG. 3) of the tape bearing surface of the trailing outerportion 312 is adapted for skiving air from the magnetic medium when themagnetic medium travels as shown. The guides are oriented relative tothe tape bearing surface of the nearest portion of the head with no wrapor a slight underwrap angle β (as shown in FIG. 3), which directs themedium to fly over the leading outer portion 310 with minimal (e.g.,less than the at-rest) or no contact. The tape engages the leading edge322 of the tape bearing surface of the central portion, and engages theinner edge of the tape bearing surface of a trailing one of the outerportions. An illustrative angle β between the medium in tensionextending from the guide to the nearest outer portion and the tapebearing surface of the outer portion may be 0° to about 0.75°.

Thus, tape wrapping at edges of the tape bearing surfaces of the variousportions in use is minimized, which in turn reduces the aforementionedproblems of running friction and acoustic-like waves.

With continued reference to FIG. 4, the outer edge 324 of the tapebearing surface of the leading outer portion 310 is non-skiving, i.e.,the outer edge of the leading outer portion does not skive air from themedium. This is a result of the guides being positioned as noted above.This is because the tape is spaced from the outer edge of the leadingouter portion (slightly underwrapped), an air wedge develops, causingthe medium to fly above the inner edge 318 of the leading outer portion.

Alternatively or to further enhance the formation of the air wedge, theouter edges of the tape bearing surfaces of the outer portions may beshaped, e.g. having a beveled edge 350 as shown on the outer portion 312of FIG. 3. The beveled edge 350 encourages formation of an air wedgebetween the tape and the tape bearing surface, thereby allowing abroader set of approach angles for the tape, and/or allowing use of ano-wrap or even slightly overwrapped design where the tape approachesthe leading outer portion in a plane parallel to or nearly parallel tothe tape bearing surface of the leading outer portion.

The medium peels off the trailing outer portion 312 as it approaches theouter edge 326 of the trailing outer portion. Thus, little or no runningfriction is observed at the outer edge 326 of the trailing outerportion. It should also be noted that guide position is generallyadjusted to ensure that the medium does not peel off so close to thedownstream transducers that an intolerable spacing loss occurs.

Referring to FIG. 5, it is seen that when the direction of medium travelis reversed, a similar effect is observed at the now-leading outerportion 312 and now-trailing outer portion 310.

In one embodiment, at least one of the portions has patterning forinducing the magnetic medium to fly thereover in an area away from thetransducers and/or to reduce stiction of the medium to the tape bearingsurface of the portion (as compared to a smooth, planar tape bearingsurface). Examples of patterning include texturing, beveling of sectionsof the tape bearing surface edge, formation of ridges or ribs thereon,formation of channels therein, etc. FIGS. 6 and 7 illustrate an exampleof a central portion 316 having patterning as can be achieved by tapelapping. In a tape lapping process, a tape having abrasive sections,e.g., of diamond, alumina, etc. is drawn over the portion to selectivelyabrade areas thereof. In this example, the abrasive tape would haveabrasive strips flanking a central nonabrasive strip. As shown in theexample of FIGS. 6 and 7, areas 328 of edges of the tape bearing surface330 not aligned with the transducers 332 become beveled. The bevelingpromotes entrainment of air between the medium and the tape bearingsurface. The sections of the edges of the tape bearing surface alignedwith the transducers is not significantly affected by the tape lapping,and therefore retains its ability to skive air from the tape. In oneillustrative embodiment, the central portion and outer portions havepatterning with physical characteristics of being lapped by tapelapping.

In a read-write-read (R-W-R) configuration, outer reading portions flanka single writing portion. As the name implies, the outer portionsinclude one or more arrays of readers, while the center portion includesone or more arrays of writers. Variations on the head include a R-W-Rhead, a R-R-W head, a W-W-R head, etc.

One or more servo readers may be positioned on one or more of the outerportions, the central portion, or a combination thereof. In oneembodiment of a R-W-R configured head, the array of transducers of thecentral portion includes a plurality of writers and at least one servoreader calibrated to the position of one or more of the writers of thecentral portion. Such an embodiment exhibits better positioning oftracks during writing. The ability to position the tracks moreaccurately enables inclusion of more tracks on the tape, which maytranslate into higher areal density.

Any known method of calibrating the servo to one or more nearbytransducers may be used. For example, the calibration may be performedmagnetically, optically, etc. e.g., to determine a physical spacingbetween the servo and the transducer(s). Logic in the system then usesthis measurement to precisely position the head relative to the servotracks on the medium.

The position of the guides may be adjustable or fixed. Thus, in someapproaches, the position of the guides may be set during manufacture andfixed, while in others the guides may be adjusted in the field, while inyet others, the guides may be set during manufacture and can be lateradjusted in the field. Any known mechanism to fix the guides or makethem adjustable may be used.

A method for setting a wrap angle according to one embodiment includesadjusting a guide position to overwrap a magnetic tape over an outeredge of a leading outer portion. For example, in FIG. 5, the guide 304may be positioned to create an overwrap at edge 324. The trailing guide306 may or may not be in an overwrap configuration. The magnetic tape ispassed over the head, the tape traveling in a direction from the leadingouter portion towards the trailing outer portion. The magnetic tape isread using the leading outer portion, and a wrap angle of the magnetictape relative to the leading outer portion is adjusted until the tape isno longer readable. For example, the guide 304 may be raised up untilthe tape pops off of the leading outer portion 310. The position of theguide when the tape becomes no longer readable is determined. Typically,this will correspond to a wrap angle β of about 0°. The “in use” wrapangle β, to be used for data storage operations, is selected based onthe determined position of the guide, and the guide is set to providethe selected wrap angle. As noted above, an illustrative “in use” wrapangle β between the medium in tension extending from the guide to thenearest outer portion and the tape bearing surface of the outer portionmay be 0° to about 0.75°, but could be higher. Thus, the selected wrapangle may be the same as or greater than the wrap angle provided by theguide when the tape becomes no longer readable.

Conventional fabrication techniques may be used to create the variousembodiments, such as thin film processing, lapping, etc.

FIG. 8 illustrates a simplified tape drive which may be employed in thecontext of the present invention. While one specific implementation of atape drive is shown in FIG. 8, it should be noted that the embodimentsof the previous figures may be implemented in the context of any type oftape drive system.

As shown, a tape supply cartridge 820 and a take-up reel 821 areprovided to support a tape 822. These may form part of a removablecassette and are not necessarily part of the system. Guides 825 guidethe tape 822 across a preferably bidirectional tape head 826, of thetype disclosed herein. Such tape head 826 is in turn coupled to acontroller assembly 828 via a write-read cable 830. The controller 828,in turn, controls head functions such as servo following, writing,reading, etc. An actuator 832 controls position of the head 826 relativeto the tape 822.

A tape drive, such as that illustrated in FIG. 8, includes drivemotor(s) to drive the tape supply cartridge 820 and the take-up reel 821to move the tape 822 linearly over the head 826. The tape drive alsoincludes a read/write channel to transmit data to the head 826 to berecorded on the tape 822 and to receive data read by the head 826 fromthe tape 822. An interface is also provided for communication betweenthe tape drive and a host (integral or external) to send and receive thedata and for controlling the operation of the tape drive andcommunicating the status of the tape drive to the host, all as will beunderstood by those of skill in the art.

In one example of use, a magnetic data storage system guides a magneticmedium over a magnetic head at an angle at which the magnetic mediumflies over a leading outer portion of the head, engages a leading edgeof a tape bearing surface of a central portion of the head, and engagesan inner edge of a tape bearing surface of a trailing outer portion ofthe head, where the inner edge of the tape bearing surface of thetrailing outer portions skives air from the magnetic medium when themagnetic medium travels in a direction from the central portion towardsthe trailing outer portion.

While various embodiments have been described above, it should beunderstood that they have been presented by way of example only, and notlimitation. Thus, the breadth and scope of a preferred embodiment shouldnot be limited by any of the above-described exemplary embodiments, butshould be defined only in accordance with the following claims and theirequivalents.

What is claimed is:
 1. A drive-implemented method, comprising: guiding amagnetic medium over a magnetic head at an angle at which the magneticmedium flies over a leading outer portion of the head, engages a leadingedge of a tape bearing surface of a central portion of the head, andengages an inner edge of a tape bearing surface of a trailing outerportion of the head, wherein the inner edge of the tape bearing surfaceof the trailing outer portions skives air from the magnetic medium whenthe magnetic medium travels in a direction from the central portiontowards the trailing outer portion.
 2. The method as recited in claim 1,wherein outer edges of the tape bearing surfaces of the outer portionsare non-skiving.
 3. The method as recited in claim 1, wherein outeredges of the tape bearing surfaces of the outer portions are beveled. 4.The method as recited in claim 1, wherein an array of transducers of thecentral portion includes a plurality of writers and at least one servoreader calibrated to the position of one or more of the writers of thecentral portion.
 5. The method as recited in claim 1, wherein at leastone of the portions has patterning for at least one of inducing themagnetic medium to fly thereover in an area away from transducersthereof and reducing stiction of the medium to the tape bearing surfaceof the at least one portion.
 6. The method as recited in claim 1,wherein the magnetic medium contacts the tape bearing surface of thecentral portion and only the inner edge of each of the tape bearingsurfaces of the outer portions when the magnetic medium is not in motionand is extended across the head.
 7. The method as recited in claim 1,wherein the central portion includes an array of writers, wherein theouter portions each have an array of readers.
 8. The method as recitedin claim 1, wherein the tape bearing surface of the central portion isplanar.
 9. The method as recited in claim 1, wherein an angle is formedbetween the tape and the tape bearing surface of each of the outerportions such that the distance between the tape and the respective tapebearing surface increases from the associated skiving edge to an outeredge of the respective tape bearing surface when the tape is at rest andin tension.
 10. The method as recited in claim 1, wherein each outerportion has an array of transducers selected from a group consisting ofreaders and writers; wherein the central portion has a planar tapebearing surface and an array of transducers selected from a groupconsisting of readers and writers; wherein the tape bearing surface ofeach outer portion has a tape-engaging section configured and arrangedrelative to the tape bearing surface of the central portion to at leastsometimes have contact with a tape passing thereover during normal use,wherein an inner edge of each tape bearing surface of the outer portionis physically oriented with respect to the tape bearing surface of thecentral portion to skive air from the tape when the tape travels in adirection from the central portion towards the respective outer portion,and wherein an angle is formed between the tape and the tape bearingsurface of each outer portion such that the distance between the tapeand the respective tape bearing surface increases from the inner edge toan outer edge of the tape bearing surface of the respective outerportion when the tape is at rest and in tension.
 11. A method forsetting a wrap angle, comprising: adjusting a guide position to overwrapa magnetic tape over an outer edge of a leading outer potion of amagnetic head having the leading outer portion, a trailing outerportion, and a central portion positioned between the outer portions,each portion having a tape bearing surface and an array of transducersselected from a group consisting of readers and writers; causing themagnetic tape to pass over the head, the tape traveling in a directionfrom the leading outer portion towards the trailing outer portion;causing reading of the magnetic tape using the leading outer portion;adjusting a wrap angle of the magnetic tape relative to the leadingouter portion until the tape is no longer readable; determining aposition of the guide when the tape becomes no longer readable;selecting a wrap angle based on the determined position of the guide;and setting the guide to provide the selected wrap angle.
 12. The methodas recited in claim 11, wherein the selected wrap angle is greater thana wrap angle provided by the guide when the tape becomes no longerreadable.
 13. The method as recited in claim 11, wherein outer edges ofthe tape bearing surfaces of the outer portions are non-skiving.
 14. Themethod as recited in claim 11, wherein outer edges of the tape bearingsurfaces of the outer portions are beveled.
 15. The method as recited inclaim 11, wherein at least one of the portions has patterning for atleast one of inducing the magnetic tape to fly thereover in an area awayfrom the transducers and reducing stiction of the tape to the tapebearing surface of the at least one portion.
 16. The method as recitedin claim 15, wherein the patterning has physical characteristics ofbeing lapped by tape lapping.
 17. The method as recited in claim 11,wherein the magnetic tape contacts the tape bearing surface of thecentral portion and only an inner edge of each of the tape bearingsurfaces of the outer portions when the magnetic tape is not in motionand is extended across the head when the guide is set to provide theselected wrap angle.
 18. The method as recited in claim 11, wherein thecentral portion includes an array of writers, wherein the outer portionseach have an array of readers.
 19. The method as recited in claim 11,wherein the tape bearing surface of a central portion is planar.
 20. Themethod as recited in claim 11, wherein, when the guide is set to providethe selected wrap angle, an angle is formed between the tape bearingsurface of each of the outer portions such that the distance between thetape and the respective tape bearing surface increases from theassociated skiving edge to an outer edge of the respective tape bearingsurface when the tape is at rest and in tension.